Editing Divergent boundary (section)

{{short description|Linear feature that exists between two tectonic plates that are moving away from each other}}
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[[File:Continental-continental constructive plate boundary.svg|thumb|upright=1.4|Continental-continental divergent/constructive boundary]]
[[File:Mid-ocean ridge cut away view.png|thumb|upright=1.35|Oceanic divergent boundary: mid-ocean ridge (cross-section/cut-away view)]]
In [[plate tectonics]], a '''divergent boundary''' or '''divergent plate boundary''' (also known as a '''constructive boundary''' or an '''extensional boundary''') is a linear feature that exists between two [[List of tectonic plates|tectonic plates]] that are moving away from each other. Divergent boundaries within [[continent]]s initially produce [[rift (geology)|rifts]], which eventually become [[rift valley]]s.  Most active divergent plate boundaries occur between [[Oceanic crust|oceanic plate]]s and exist as [[mid-oceanic ridge]]s.<ref>{{Cite book | doi=10.1029/GM071p0183| chapter=Petrological Systematics of Mid-Ocean Ridge Basalts: Constraints on Melt Generation Beneath Ocean Ridges| title=Mantle Flow and Melt Generation at Mid-Ocean Ridges| pages=183–280| series=Geophysical Monograph Series| year=2013| last1=Langmuir| first1=Charles H.| last2=Klein| first2=Emily M.| last3=Plank| first3=Terry| isbn=9781118663875| hdl=10161/8316}}</ref><ref>{{Cite journal |doi = 10.1029/91JB02508|title = Mid-ocean ridge magma chambers|journal = Journal of Geophysical Research|volume = 97|issue = B1|pages = 197|year = 1992|last1 = Sinton|first1 = John M.|last2 = Detrick|first2 = Robert S.|bibcode = 1992JGR....97..197S}}</ref>

Current research indicates that complex [[convection]] within the [[Earth's mantle]] allows material to rise to the base of the [[lithosphere]] beneath each divergent plate boundary.<ref>{{cite journal | author1 = Toshiro Tanimoto |author2= Thorne Lay |authorlink2=Thorne Lay| date = November 7, 2000 | title = Mantle dynamics and seismic tomography | journal =Proc. Natl. Acad. Sci. U.S.A. | volume =97 | issue =23 | pages = 12409–10 | doi = 10.1073/pnas.210382197 | pmid = 11035784 | pmc = 34063 | bibcode=2000PNAS...9712409T|doi-access= free }}</ref>{{Failed verification|date=September 2024}}
This supplies the area with huge amounts of heat and a reduction in pressure that melts [[Rock (geology)|rock]] from the [[asthenosphere]] (or [[upper mantle (Earth)|upper mantle]]) beneath the rift area, forming large [[flood basalt]] or lava flows. Each eruption occurs in only a part of the plate boundary at any one time, but when it does occur, it fills in the opening gap as the two opposing plates move away from each other.

Over millions of years, tectonic plates may move many hundreds of kilometers away from both sides of a divergent plate boundary. Because of this, rocks closest to a boundary are younger than rocks further away on the same plate.